This invention relates to downhole tools used in fishing operations. Milling shoes, sometimes known as rotary shoes, are used in fishing operations to cut away metal, formation or cement to release a tool that is stuck in a wellbore. The typical milling shoe is a fairly short tubular that is threaded at one end and has cutting material on the side of the shoe at the other end. These milling shoes are useful in removing stuck downhole tools during fishing operations.
During fishing operations to recover stuck or broken members from the well bore using coil tubing or conventional jointed tubing pipe it is sometimes necessary to cut over the fish using a milling shoe at the bottom of the fishing string and let it feed upwards into a larger pipe called a wash-pipe. But the fish will not feed upwards into the wash-pipe very far past the milling shoe at the bottom especially when cutting over broken off coil tubing because the broken off coil tubing keeps breaking off and jamming in the wash-pipe above the milling shoe such that the inventor has found that it becomes impossible to mill any further after the jam occurs.
There exists a Bowen mill extension with a tapered throat faced with Itcoloy™ for milling away a flared or jagged fish to enable the fish to pass up into and be engaged by a grapple in a bowl above the mill extension. However, the Bowen mill extension does not solve the problem of jammed coil tubing because the tapered throat restricts the bore. In addition, the Bowen mill extension requires a grapple and bowl above the mill extension.